Process for the manufacture of fibers and filaments of linear polyesters having improved properties



Oct. 15, 1963 H. KURZKE ETAL PRocEss EoR THE MANUEACTURE oF EIBERS AND FILANENTsoF LINEAR PoLYEsTERs HAVING IMPRovED PROPERTIES Filed Aug. 8, 1961 f ESE@ SEHEN Q\ ERAN@ United States Patent O PROCESS FOR THE MANUFACTURE F HEERE) AND FLAMENTS 0F LINEAR POLYESTERS HAVING IMPRGVED PRGPERTES Herbert Kui'zke, Helmut Sattler, and Edmund Stix, all of Bobingen, near Augsburg, Germany, assignors to Farb- Wei'ke Hoechst Aktiengesellschaft vormals Meister Lucius z Brning, Frankfurt am Main, Germany, a corporation ci Germany Filed Ang. 8, 1961, Ser. No. 1129,979 Claims priority, application Germany Aug. i3, 1960 8 Claims. (Cl. ifi-4S) The present invention relates to the manufacture of iibers or filaments `of linear aromatic polyesters land more particularly it relates to the lmanufacture of fibers and filaments of linear aromatic polyesters having improved properties.

The present invention provides `a process for making fibers and filaments of linear aromatic polyesters which have a good dyeability. Moreover, the present invention provides a process for making fibers and filaments of linear momatic polyesters having a low tendency to pilling.

Fibers or filaments of linear polyesters, especially of polyethylene terephthalate, possess a number of special advantages but, in addition thereto, they have the `disadvantage that they are dithcult to dye. Hitherto, the ii-bers or filaments have mostly been dyed with the use of so-called carriers and with the application of especially high temperature. These dyeing methods require special care and need expensive apparatus, particularly when piece goods are to be dyed.

lt has now been found that bers and filaments can :be produced in simple manner and in continuous `operation from linear polyesters, and especially from polyethylene terephthalate, which possess a considerably improved dyeability.

The present invention is concerned with a process for the manufacture of fibers and filaments of linear polyesters having an improved dyeability. A spinning cable or filament of linear polyesters, especially of polyethylene terephthalate, or of a mixed polyester, is stretched under cold and/ or heated conditions in one or several stages to a lmultiple of its original length, then allowed to shrink by 8 to 40% at a temperature above 190 C., preferably -at 220 C., and subsequently stretched a second time under cold and/ or heated conditions lby at least 3% and at most up to the breaking limit of the cable or filament.

It is ysuitable to use a spinning cable of polyethylene terephthalate having for example a total titer of several hundred thousand denier and to stretch said cable in steam, hot water or hot air to a multiple of its original length with the aid of known roller units. The degree of stretching can vary within wide limits, depending on the intended application or the desired textile properties of the tiber. Instead of carrying out the stretching in steam or hot air, it can be realized in exceptional cases without the action of heat in the cold.

The shrinking process, which is carried out after the stretching, is preferably performed with the aid of hot air or by conducting the cable over ,a heated surface.

VThe lower temperature limit shall not be lower than '190 C. The temperature given is, as in the stretching, the temperature of the heat transferring medium. The upper temperature limit in the shrinking process is at most 250 C. for fibers and up to 310 C. for filaments that are treated for a short period of time.

The admissible shrinkage in the shrinking process is 840%, depending on the properties of the material used for making the fibers (for example the specific viscosity of the polyester) or the chosen stretching conditions.`

ICC

When a low viscous starting material is used and with a stretching ratio of 113.8, the shrinkage is only 10%, while in the case of a highly viscous material and with a stretching ratio of 114.2. the rfiber can be allowed to shrink by 30%.

The cable which has been allowed to shrink in this manner has an especially improved dyeability. Moreover, the fibers obtained practically do not undergo further shrinkage in 'boiling water or in hot air, provided that the air temperature is not higher than the temperature in the shrinking process. If the fibers were thermally treated at the indicated temperature without being allowed to shrink, their dyeability could be immaterially improved only.

Finally, the cable is again stretched under cold and/.or heated conditions. The stretching -degree ranges trom 3% up to the breaking limit of the cable. By the selection or" the stretching ratio and the kind of stretching, with steam, under hot or cold conditions, fibers or lilanients can be obtained having the desired shrinking values for a definite application. The shrinking values of the fibers or filaments on boiling in Water can range from 0 to 20% and on heating in hot air of 200 C. they can range from 2 to 30%.

lt is surprising that by the after-stretching process (second stretching) the improved dyeability -obtained 'by the shrinking is not impaired. Thus it is possible to produce by the process of the invention iibers and filaments of polyethylene terephthalate having an especially good dyeability, good physical properties, an :adjustable shrinkage in boiling water and an adjustable thermoshrinkage.

When fibers or filaments having dierent shrinking properties are worked up together very voluminous yarns can be obtained (bulk yarns).

For the manufacture of fibers and filaments of linear polyesters, especially yof polyethylene terephthalate, there are generally used polymers having an average molecular weight corresponding to a specific viscosity of 0.78-0.84. The specific viscosity is the ratio, reduced by 1, of the viscosity of the solution of the polyester in a mixture of 60 parts of phenol and 40 parts of tetrachloroethane to the viscosity of the solvent, the viscosities being determined by the time a lixed volume needs to flow through an Ubbelohde viscometer.

Recently, fibers land filaments |having favorable properties, for example a low tendency to pilling, are made from polyethylene terephthalate of low medium molecular weight. However, fibers of this -kind are more difficult to dye by various dyestuis than fibers of polyethylene terephthalate having the usual medium molecular Weight. Y

Moreover, it has been found that little pilling occurs and well dyeable `fibers and filaments can be made by the process of the invention when the fibers or filaments are produced from polyethylene terephthalate having a specific viscosity below 0.5. It `is remarkable that the fibers and filaments of polyethylene terephthalate having a specific viscosity below 0.5, which have been produced by the process of the invention, can be dyed more easily than products that-have been made in the same manner from polyethylene terephthalate having a specific viscosity of 078-084. This could not be expected since the dyeability of fibers and filaments produced by the usual manufacturing process diminishes with a series of dyestuifs as the medium molecular Weight, i.e. the lspecic viscosity, decreases. Thus it is of advantage, not only `on account of the improved textile .properties but also in View of the still further improved dyeability, to use in the manufacture of the fibers and filaments used in the present process polyethylene terephthalate having an especially low medium molecular weight, corresponding to ta specific viscosity be-low 0.5.

When Ylibers and filaments from polyethylene terephthalate having an especially low medium molecular Weight, are spun and worked up, the final products o'btained may have defects, for example agglutinating individual lfibers and drop-like knots, which imp-air the further Working up of the fibers and iilaments into textile materials.

These defects result from the fact that the individual filaments leaving the spinning nozzle of polyethylene terephthalate having a -low medium molecular weight are not so tough as filaments of normal polyethylene terephthalate leaving lthe nozzle 'and thus agglutinate more readily with one another. A preferred embodiment of the process of the invention `consists in spinning polyethylene terephthalate having a lvery lour medium molecular weight, corresponding to la specific viscosity below 0.5 in adrnixture with a small proportion of up to 20%, and preferably of polyethylene terephthalate having a normal medium molecular weight and a specific viscosity in the range from 0.78 to 0.84, and treating the fibers and filaments obtained Ias described above. By this mode of operation the textile properties of the bers and laments are not modified and their dyeability is not impaired, but the spinning process is facilitated and fewer agglutinations and other defects can be observed.

Polyethylene terephthalate having a very low medium molecular Weight is often obtained in the polycondensation with a non uniform distribution of the molecular Weight, so that when spinning from the melt `the individual filaments leaving the spinning nozzle have a non -uniform toughness in themselves and against one another whereby filaments of varying thickness as well as knots may be formed. This diiculty can be overcome by melting polyethylene terephthalate having a specific viscosity below 0.5, Vprior to spinning the fibers from the melt, in a known `dev-ice with the exclusion of air, extruding it into a Wire some millimeters thick, cutting the wire into chips and feeding the chips to the -spinning unit. By this pretreatment the polyethylene terephthalate is homogenized and intimately mixed. Either mode of operation, namely the admixture of a small proportion of polyethylene terephthalate having a normal medium molecular weight or the homogenization of the polyethylene terephthalate by melting it Yprior `to the spinning process overcomes the above disadvantages when applied individually or jointly. It is especially advantageous to mix polyethylene terephthalate having a specific viscosity -below 0.5 with a small proportion of up to and preferably 10%, of polyethylene terephthalate having a normal medium molecular weight, i.e. a specific viscosity in the range from 0.78 to 0.84, to melt the mixture obtained in a known device -with the exclusion of air, to form a -Wire having a thickness of several millimeters by extrusion, to cut Ythe Wire into chips and to feed the chips to the actual spinning device for being spun from the melt. By `this pretreatment the mixture of the two polyethylene terephthalates is homogenized and the favorable action of the proportion of polyethylene terephthallate having a normal medium molecular Weight is improved. By this pretreatment the number of spinning defects in the final product is further reduced.

For uniformly heating the cable of fibers or filaments it is passed over a heated 4surface while being in contact therewith. If the temperature of the surface is too high, the fibers and filaments may adhere to the heated surface. This is favored by the Yfact that the material is under a 'slight tension on account of the shrinkage. The adhering bers soil the heated surface of the heating device and above all, they disturb the further working up of the fibers. vIn general it is, therefore, not recommended to heat the surface at a temperature above 220 C.

However, the temperature of the heated surface, the temperature of the fibrous material and the degree of shrinkage can be surprisingly increased when the surface over which the cable of bers or filaments is passed after the iirst stretching to undergo shrinkage is coated with a thin, smooth layer of a material having poor heat-conducting properties. A coating of this kind prevents the fibers or filaments 4from adhering to the surface of contact and, furthermore, in such a thin, smooth layer having poor heat-conducting properties a temperature gradient is formed which results in a more uniform heating of the cable of bers than in case the cable contacts directly the metallic heating surface. By the process of the invention the fiber cable is heated to a higher temperature and more uniformly so that it can then be dyed more intensely and more uniformly and is substantially free from agglutinations.

As layers having poor heat-conducting properties there can be used narrow and wide-meshed fabrics of temperature resisting materials, and heatproof closed or perforated lms.

According to a preferred embodiment of the process of the invention the heated surface, over which the filamentsor cable of bers are passed, is ycoa-ted with a fabric of endless glass laments or yarns of glass fibers. This fabric forms a thin and smooth layer having poor heat conducting properties that withstands the temperatures applied and the friction of the liber cable.

in order to avoid losses of heat and to maintain constant the desired temperature, it is often of 'advantage to arrange a heated plate above the heated surface, which plate, however, does not come into contact with the fiber cable.

Moreover, it is of advantage carefully to dry the fiber cable before it enters the heated shrinking zone. Thus heating energy is lsaved in the shrinking zone and the liber cable really picks up the temperature of the heated surface `covered with a fabric of endless 'glass filaments or yarns of glass fibers. Furthermore, the danger of the hydrolytic decomposition of the polyester by water at 4the high temperature of the heating device is reduced. rIlhe cable can be dried according to common methods, for example by passing it over a surface heated at a temperature above C. or by heating internally the conveying rollers of the cable.

The following examples serve to illustrate the invention but they are not intended -to limit it thereto. In the examples the medium molecular weight or the polymerization degree of the polyethylene terephthalate used is defined by the specific viscosity D, determined with a 1% solution of the polymer in a mixture of 60 parts of phenol and 40 parts of tetrachloroethane in an Ubbelohde viscometer. The specific viscosity is the ratio minus 1 of the viscosity of the solution of the polymer to the viscosity of the solvent. Y

For determining the dyestu receptivity 20 grams of the liber sample were boiled -for one hour in 1 liter of a bath containing 3%, calculated on the weight of the sample, of the dyestuff obtained by brominating 1,5diamino4,8di hydroXy-anthraquinone. The residual dyestut in the bath was determined by ycolorimetric means and the dyestul receptivity of the sample was calculated in percent of the dyestuif used.

The process of the invention is better shown in FIG- URES 1 and 2 of the drawing. The temperatures, rotational speed of the rolls `and other values set forth on the drawing are taken from Example '4 of the specification. As shown by the legends in FIGURE 1, the unstretched filament cable is first stretched with steam between rolls wherein the `second set of rolls rotates at a faster rate of speed than the rst set. The cable is then shrunk under heated conditions with the use of the heat barrier assembly shown better in FIGURE 2. The set of rolls drawing the cable through the shrinking unit rotates -at a slower rate of speed than the set feeding the cable through the shrinking unit. The cable is then stretched a second time under heated conditions with Ithe use of ythe heat barrier unit of FIGURE 2. However, in this stage of the second stretching, the layer of Fiberglas tissue can be omitted if desired. The iinal set of rolls drawing the cable to the second stretching station is rotated at .a faster r.p.m. than the set of rolls feeding the cable to the second stretching station.

The heat barrier unit of FIGURE 2 is self-explanatory from an examination ot the legends of the gure. Here, the cable being treated passes in contact with a Fiberglas layer which overlies a heating block. A heat barrier sheet is positioned in spaced-apart relationship above the Fiberglas sheet and the assumed path of the cable.

EXAMPLE 1 A spinning thread of 180 denier composed of 25 individual -iilaments of polyethylene terephthalate having a specific viscosity ns1, of 0.84 was continuously stretched at 110 C. as usual to 4 times its original length with contact heating, and wound up on a'bobbin. The .thread was then passed, at a rate of 30 meters per minute, into a heating ue having a length `of 20 cm. and a temperature of 250 C., in which it was allowed to shrink by 30% calculated on Ithe feed rate, by the following conveying means. The thread was fthen stretched continuously in the cold to its original length. Prior to the shrinkage and in the nal state the thread had the following textile properties:

stretched thread Final State prior to shrinkage Titel- 45.7 denier 44.9 denier. Tensile strength 4.0 g/denier. Elongation at break 1 7 0.3%. shrinkage at 200 C 23.5%. Dyestuf reeeptivity 43.5%

EXAMPLE 2 EXAMPLE 3 A spinning cable was produced `from the polyethylene terephthalate defined in Example 2 having a total titer of 340,000 denier and a spinning -titer of fthe individual iilaments of 5.1 denier. The cable was treated as described in Example 2. The data and the textile properties of the nal product are given in the Afollowing Table 1.

EXAMPLE 4 A spinning cable having a total titer of 370,000 denier and a spinning titer 'of the individual filaments of 11.7 denier Was made from polyethylene tereph-thalate having a specic viscosity usp of 0.545 and the ycable was treated as described in Example 2. The data and tex-tile properties of the cable are listed in the vfollowing Table 1.

In the following table the data and textile properties of the cables are compared with the data and properties of a cable as defined in Example 2 which was stretched but not allowed to Shrink.

Table 1 Example No. 2 3 4 Comparison n.9 of polymer 0. 0.80 0. 545 0. 80 Total titer of cable, denier 370 000 340,000 370, 000 370.000 Titer of individual lament, denier 7 11 11. 7 Conveying speed in m/minute:

Prior to stretching 10.1 10. 5 10. 5 10. 1

After stretching 45. 3 43.6 43.5 45. 3

After shrinkage 34. 7 33. 6

After second stretching 37. 8 38. 4 Temperature, C.:

During shrinkage 240 240 During second stretching 120 150 Individual titer, denier 3. 4 1. 6 Tensile strength g/denier 4. 7 5. 2 Elongation at break, percent 56 33. 5 shrinkage at 200 C., percent-- 4.1 7. 3 Dyestut receptivity, perccnt 41. 7 39. 7

The above rfable 1 shows that the process of the invention permits the manu-facture of liilamenlts and fibers of polyethylene terephthalate having a consider-ably improved dyestui receptivity, the other textile values remaining the same.

EXAMPLE 5 Polyethylene terephthalate having a specific viscosity 115D of 0.46 Iwas spun from the melt and a spinning cable was formed having a total titer of 600,000 denier and a spinning titer (unstretched titer) of the individual laments of 11.7 denier. The `cable was stretched as described in Example 2, then continuously allowed to shrink while being heated by contact heating, and subsequently stretched again while heated. The cable was then treated With a scrooping agent, crimped and cut. The conveying speeds in the individual stages and the textile properties of the inal product are listed in the following Table 2.

EXAMPLE 6 A mixture of parts of polyethylene yterephthalate having a speciic viscosity 75p of 0.46 and 10 par-ts of polyethylene terephthalate having a specific viscosity asp of 0.82 was spun from the melt and a spinning cable was Iformed having a total titer of 150,000 denier with a spinning titer of the individual filaments of 11.8 denier. The cable was treated as described in Example 5. The data and textile properties lof the final product are recited in the following Table 2. A comparison with Example 5 reveals that with the dyestuff receptivity the number of spinning defects is iconsiderably lower when the present mixture was used instead `of a polyethylene terephthalate having a very 10W medium molecular weight.

EXAMPLE 7 A mixture of 90 parts of polyethylene -terephthalate having a specific viscosity 1751, -of 0.47 and 10 parts of polyethylene terephthalate having a specific viscosity risp lof 0.82 was melted at 260 C. in a melting device with the lexclusion of air and with an extruder a wire having a ldiameter of 3 mm. Was made. This wire -Was cut into 4 mm. long pieces which were fed to a melt spinning apparatus.

From the fibers a spin-ning cable was orrned havin-g total titer of 165,000 denier, While the individual ibers had a spinning titer of 11.7 denier. as described in Example 5. The `data and textile properties of the cable are indicated in the following Table 2. A comparison with Examples 5 and 6 reveals that with a dyestui receptivity lof 52% the lowest number of spinning defects is lobtained when 90 parts of polyethylene terephthalate having an especially low medium molecular weight are mixed with l0 parts of polyethylene terephthalate having a normal medium molecular weight, the mixture is melted and homogenized `and the product obtained is then spun from the melt.

'Ihe cable was treated v 7 The number of defects", `the agglutinations or drop-like knots in the final product were determined by taking samples.

invention have good textile and tinctorial properties and, furthermore, they have little orfno tendency to pilling, this being very important in textile industries.

Table 2 Example No 5 6 7 113D of polymer 100%, 0.46.. 90%, 0.46; 10%, 90 0.47 previously; 10%,

- v 0.82. 0.82 homogenized.

Tlter of spinning cable, denier-- 600,000 150, 000 165, 000. Spinning titer of individual filaments, denier.. 11.7 .S 11.7. Conveying speeds, meters per minute:

Prior to stretchi.ng 10.1 10.0 10.0

After stretching 40. 4 41. 6 41. 5

After shrinkage 35.4 36. 2 36. 0

After second stretching"- 39. Q 41. 41. 2 Temperature. C.:

During shrinkage. 234 233 233.

During second stretching. 150 155 155. Individual titer, denier. 3. 3 3.2 3.3. Tensile strength, gJdenier- 2. 8- 3.0 3.1. Elongation at break, percent 4R 4 2 46. shrinkage at 200 C. percent- 2. 4 7. 4 5.3. Dyestu receptivity, percent 61 61 52. Number of spinning defects per 100 ki1ograms 25 6. 8 4. 9.

of material.

EXAMPLE 8 We claim:

A spinning cable having la total titer of 100,000 denier and a spinning titer (titer of -unstretched individual rilaments) of 11.7 denier Eof polyethylene terephthalate having a specific viscosity '175D of 0.82 was stretched in steam, continuously allowed to shrink while being heated with Contact heating and then stretched again while heated under contact. The cable was then treated with a scrooping agent, crimped and cut. The contact heating for the shrinkage after the iirst stretching took place on a rn. long vaulted surface which was heated at 245 C. and covered-with a layer of glass silk (7 filaments/cm. in chain and warp, 290 grams per square meter). At a distance of a second heated surface which was likewise heated at 245 C. but did not touch the ber cable was placed `opposite the iirst one.

The conveying speeds of the individual stages and .temperatures as well Ias the dye receptivity of the tinal product are given in the -following Table 3. In said table the values are compared with the values `of a material which had been produced in the same manner with the exception that Kthe iiber cable Idirectly contacted the heated metallic surface during the shrinking process. Thus, -the temperature of 'the heating device had to be lower and the degree of shrinkage the cable underwent was likewise lower. This resulted in not so high a dyestuff receptrvity of the treated bers.

Table 3 Example 8 Comparison n,... of polymer. 0.8 0. Titer of spinning cable denier 100, 000 100, 000 Spinning titer of individual laments, denier-- 11. 11. Conveying speeds, meters per minute:

Prior to stretching 10.4 10. 0 After stretching- 46. 4 44. 6 After shrinkage. 35. 2 35. 5 After second stretch 38. 5 38. 7 Relative shrinkage, calculated on the co veying speed after shrinkage, percent 31 25 Temperature of the heating surfaces, C.:

For the shrinkage 245 215 For the second stretching 100 100 Dyestut receptivity, percent 42 25 It is obvious from the above table that the `application of a thin and smooth layer having poor heat-conducting propenties to the heating surface involves an increase of the dyestufr" receptivity from 25% to 42%, for example, without agglutinations of the bers occurring.

The fibers and laments treated by the process of the 1. A process for the manufacture of vfilamentous structures of polyethylene terephthalate which have an timproved dyeability which comprises stretching the filamentous structures to a multiple of their original length, shrinking the ilamentous structures by 8 to 40% at a temperature above C.; and then stretching the iilamentous structures -a second time by at least 3% up to at most the breaking `limit of said filamentous structures.

2. A process for the manufacture of filamentous structures of polyethylene terephthalate which have an cimproved dyeabili-ty which comprises stretching -the lilamentous structures under heated conditions to a multiple of their original length, shrinking said structures by 8 fto 40% at'a temperature above 190 C., and stretching them a second time by -at least 3% up to at most the breaking limit `of said ilamentous structures.

3. A process Ifor the maintenance of iilamentous structures of polyethylene terephthalate which have an improved dyeability which comprises stretching the lilamentous stnlctures to a multiple of their Ioriginal length Iin several stages =under heated conditions, `shrinking said structures by 8 to 40% at a temperature above 190 C., 'and stretching them again by at least 3% up to at most the breaking limit of said structures.

4. The process of claim l wherein the structures are shrunk at 220 C.

5. The process of claim 1 wherein the filamentous structures are shrunk at a temperature above 190 C. by passing the structures in contact With a heated sur-face covered with a thin iand smooth layer having poor heatconducting properties.

6. The process of claim 5 wherein the layer is a glass ber fabric.

7. The process of claim 1 wherein said iilarnentous structures having a specific viscosity below 0.5 are treated.

8. A process as claimed in claim 1 wherein lamentous structures are prepared from a mixture of polyethylene terephthalate having a speciiic viscosity of less than 0.5, and up -to 20% Weight polyethylene terephthalate having a specific viscosity of between 0.78 and 0.84.

2,556,295 Pace June l2, 1951 FOREIGN PATENTS 586,729 Canada Nov. 1o, 1959 Adams et al Aug. 19, 1960 

1. A PROCESS FOR THE MANUFACTURE OF FILAMENTOUS STRUCTURES OF POLYETHYLENE TEREPHTHALATE WHICH HAVE AN IMPROVED DYEABILITY WHICH COMPRISES STRETCHING THE FILAMENTOUS STRUCTURES TO A MULTIPLE OF THEIR ORIGINAL LENGTH, 